Accurate identification of people is very important for law enforcement, as well as for many security and fraud-detection applications in the public and private sectors. Conventional identification methods employ high-resolution optical and infrared cameras or scanners to image the face, or read finger prints or iris patterns in the eye. These approaches work with reasonable accuracy but usually require direct, or extremely close, contact with the person to be identified: for example, by placing a hand on the scanner plate to record fingerprints, or placing one's head against a positioning-frame to allow a lens to produce a high-resolution image of the eye.
Biometric identification based on fingerprints has been widely deployed commercially in recent years for security and immigration applications, and is even being used in some personal computer systems for user login-identification. However, such systems are sensitive to the presence of dirt on the fingers, often require reapplication of the finger, and are sensitive to variants such as the pressure of the finger during the fingerprint acquisition process. Fingerprint identification can also be fooled by using artificial gummy fingers. Facial recognition methods, on the other hand, are not necessarily limited to very-close range, but the subject must generally be facing in the direction of a camera since a clear, well-lit image is required. Thus it is relatively easy to evade such systems by wearing a disguise, a face mask, or tilting the head down to avoid providing a clear image of the face. Visual face recognition methods of course depend heavily on the quality of the image, which renders such systems sensitive to range, aspect view, and illumination.
There has been increased interest in recent years for a non-contacting, remote method of identifying a person with high accuracy over distances of at least several meters. It is needed for many security, law enforcement, and intelligence gathering operations, as well as for secure access to critical computer systems. However, none of the currently available techniques can meet this need.